Is there a way to hide all particles in a scene?
Via script it would looks like this:

import bpy
for object in bpy.data.objects:
    if bpy.context.scene in object.users_scene:
        try:
            for modifier in object.modifiers:
                if modifier.type == 'PARTICLE_SYSTEM':
                    modifier.show_viewport = False
        except:
            pass


And to redisplay all particle systems in the scene:

import bpy
for object in bpy.data.objects:
    if bpy.context.scene in object.users_scene:
        try:
            for modifier in object.modifiers:
                if modifier.type == 'PARTICLE_SYSTEM':
                    modifier.show_viewport = True
        except:
            pass